Embeded circuit patterning feature selective electroless copper plating

ABSTRACT

Embodiments describe the selective electroless plating of dielectric layers. According to an embodiment, a dielectric layer is patterned to form one or more patterned surfaces. A seed layer is then selectively formed along the patterned surfaces of the dielectric layer. An electroless plating process is used to deposit metal only on the patterned surfaces of the dielectric layer. According to an embodiment, the dielectric layer is doped with an activator precursor. Laser assisted local activation is performed on the patterned surfaces of the dielectric layer in order to selectively form a seed layer only on the patterned surfaces of the dielectric layer by reducing the activator precursor to an oxidation state of zero. According to an additional embodiment, a seed layer is selectively formed on the patterned surfaces of the dielectric layer with a colloidal or ionic seeding solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of U.S.patent application Ser. No. 14/229,777, titled “Embedded CircuitPatterning Feature Selective Electroless Copper Plating”, filed Mar. 28,2014, which is presently pending, the entire contents of which is herebyincorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to the manufactureof semiconductor devices. In particular, embodiments of the presentinvention relate to selective electroless plating of dielectric layers.

BACKGROUND AND RELATED ARTS

High density interconnection (HDI) substrate patterning is typicallyperformed with semi-additive patterning (SAP). SAP requires eightprocessing steps to form each dielectric layer. First, a dielectricmaterial is formed over an existing layer. Vias are then etched throughthe dielectric layer to provide electrical connections to the lowerlayer. A seed layer is then deposited onto all exposed surfaces. Inorder to prevent metal deposition across the entire surface, a resistlayer is formed over the exposed surfaces and then patterned. Thepatterning exposes only regions of the dielectric layer on which metalis desired in order to form contact lines and contact vias. Electrolessplating then metalizes the exposed surfaces of the dielectric layer. Theresist layer may then be removed. Finally, the seed layer that wasformed over the regions that were not metallized is removed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate cross-sectional views of a process forselectively metallizing a dielectric layer having a seed layer formedwith a laser assisted local activation process according to anembodiment.

FIGS. 2A-2B illustrate cross-sectional views of a process forselectively metallizing a dielectric layer having a seed layer formedwith a colloidal seeding solution according to an embodiment.

FIG. 3 illustrates a cross-sectional view of a process for selectivelymetallizing a dielectric layer having a seed layer formed with acolloidal seeding solution according to an embodiment.

FIGS. 4A-4D illustrate cross-sectional views of a process forselectively metallizing a dielectric layer having a seed layer formedwith an ionic seeding solution according to an embodiment.

FIG. 5 illustrates an overhead view of a panel that includes multiplebuild-up structures according to an embodiment.

FIG. 6 illustrates a cross-sectional view of a device package thatincludes build-up structures according to an embodiment.

FIG. 7 illustrates a schematic diagram of a computing device thatutilizes a device package having dielectric layers formed in accordancewith in an embodiment.

DETAILED DESCRIPTION

Embodiments are directed to the selective electroless plating ofdielectric layers. According to an embodiment, a dielectric layer ispatterned to form one or more patterned surfaces. A seed layer is thenselectively formed along the patterned surfaces of the dielectric layer.An electroless plating process is used to deposit metal only on thepatterned surfaces of the dielectric layer.

According to an embodiment, the dielectric layer is doped with anactivator precursor. Laser assisted local activation is performed on thepatterned surfaces of the dielectric layer in order to selectively forma seed layer only on the patterned surfaces of the dielectric layer.According to an embodiment, after the seed layer has been formed, thedielectric layer is metallized with an electroless plating process.

According to an embodiment, the seed layer is selectively formed overthe patterned surfaces of the dielectric layer by increasing the surfacepotential of the patterned surfaces relative to the unpatternedsurfaces. In an embodiment, the surface potential of the patternedsurfaces may be increased by patterning the dielectric layer with alaser ablation process. The laser ablation process increases the surfacepotential by producing photolytic bond fissures, producing staticcharge, and increasing the surface roughness of the dielectric layer.According to an embodiment, the surface potential of the patternedsurfaces may be further increased by applying a surface treatment to thedielectric layer prior to forming the seed layer.

According to an embodiment, a seeding solution used to deposit the seedlayer onto the patterned surfaces is a colloidal seeding solution. Forexample, the colloidal seeding solution may include a mixture of PdSO₄and H₂SO₄. Such a seeding solution produces negatively charged Pdcolloids that are deposited out of the solution to form the seed layer.In such embodiments, the dielectric layer may be dipped into thecolloidal seeding solution after a surfactant has been applied to thesurface of the dielectric layer. Alternative embodiments include dippingthe dielectric layer into the colloidal solution first, and thenapplying a surfactant to the surface of the dielectric layer. Accordingto an embodiment, a reducing agent may also be applied to the surface ofthe dielectric layer in order to reduce the deposited Pd colloids thatform the seed layer to an oxidation state of zero. According to anembodiment, a colloidal seeding solution may also include a mixture ofSnCl₂ and PdCl₂. In such embodiments, negatively charged colloidscomprising Pd and Cl ions are formed. In such embodiments, excess Snions readily reduce the Pd ions to an oxidation state of zero, andtherefore, the application of a reducing agent to the surface of thedielectric layer is not required.

According to an embodiment, a seeding solution used to deposit the seedlayer onto the patterned surfaces is an ionic solution. According to anembodiment, an ionic seeding solution may include a PdCl₂ and HClsolution. In such embodiments, a reducing agent is applied to the seedlayer in order to reduce the deposited Pd ions that form the seed layerto an oxidation state of zero.

In an additional embodiment, the seed layer may be formed over theentire surface of the dielectric layer including patterned andunpatterned surfaces. In such embodiments, the adhesion strength of theseed layer formed over unpatterned surfaces is weaker than the adhesionstrength of the seed layer formed over the patterned surfaces. In suchembodiments, the seed layer formed over unpatterned surfaces is removedwith a cleaning process, such as ultra-sonic cleaning, washing with ahigh pressure water jet, or a combination of the two. According to anembodiment, the dielectric layer may be metalized with an electrolessplating process while the seed layer is still covering unpatternedsurfaces of the dielectric layer. In such embodiments, a cleaningprocess performed subsequent to the electroless plating process willremove the material plated over the unpatterned surfaces because theadhesion strength of the unpatterned surfaces is lower than the adhesionstrength of the patterned surfaces.

FIGS. 1A-1D are cross sectional views of a dielectric layer that ispatterned and metalized with an electroless process according to anembodiment that includes a dielectric layer that is doped with anactivator precursor. Laser assisted local activation of the patternedsurfaces selectively produces a seed layer on the patterned surfaces.After the seed layer has been formed, the dielectric layer is metallizedwith an electroless deposition process to selectively form metalconnections on the patterned surfaces of the dielectric layer.

Referring now to FIG. 1A, a cross section of a build-up structure 100 isshown. The build-up structure 100 includes a dielectric layer 101 formedover several electrical contacts 120. Electrical contacts 120 mayprovide electrical connections to a lower dielectric layer formed in thebuild-up structure 100. In an embodiment, dielectric layer 101 may bethe first layer of a build-up structure, and therefore, certainembodiments do not include forming the dielectric layer over existingcontacts 120. In an embodiment, the dielectric layer 101 is formed overa build-up structure core layer. According to an embodiment, thedielectric layer 101 may be an organic or inorganic material. By way ofexample, and not by way of limitation, the dielectric layer 101 may be apolyimide or an epoxy material. According to an embodiment, thedielectric layer 101 may be a resin based material. In an embodiment,dielectric layer 101 is laminated over an existing layer. In alternativeembodiments, the dielectric layer 101 may be a liquid based material,and may be spun on over the surface of an existing layer. Embodimentsinclude cured and partially cured dielectric layers 101. By way ofexample, and not by way of limitation, a partially cured dielectriclayer 101 may be approximately 90% cross-linked or greater. As shown inFIG. 1A, dielectric layer 101 has a top unpatterned surface 155.

According to an embodiment, the dielectric layer 101 may be doped withan activator precursor material that is evenly dispersed through thedielectric layer 101. The precursor material may be mixed into thedielectric material while the dielectric material is in a liquid phaseprior to being deposited onto the build-up structure 100. According toan embodiment, the doping concentration of the activator precursor maybe approximately 1% (by weight) or less. In embodiments, the activatorprecursor material is a material that includes a metallic compound thatis capable of being reduced to form a seed layer on surfaces of thedielectric layer 101. As used herein, a seed layer is a metallic layerthat functions as a catalyst for a chemical reduction of a metal thatwill be plated onto the surface of the dielectric layer 101 with anelectroless plating process. By way of example, and not by way oflimitation, the activator precursor material may be PdCl₂, PdSO₄,Pd(acac)₂, AgCl₂, or RuCl₂, Pd nano-particles, Ag nano-particles, or Cunano-particles.

Referring now to FIG. 1B, the top unpatterned surface 155 of thedielectric layer 101 is patterned with a patterning process to formpatterned surfaces 145 in the dielectric layer 101. According to anembodiment, the pattern may comprise one or more contact via openings110 that provide an opening through dielectric layer 101 to electricalcontacts 120 formed on a lower layer, one or more contact openings 112,and one or more line openings 114, or any combination thereof. Accordingto embodiments, the pattern may be formed with a patterning process suchas direct laser writing, laser projection patterning, plasma etching, orother known patterning processes.

In an embodiment, the via openings 110 may be formed with a firstpatterning process, and the contact openings 112 and the contact lineopenings 114 may be formed with a second patterning process. The firstpatterning process used to form the via openings 110 may be a differentpatterning process than the second patterning process. By way ofexample, and not by way of limitation, the first patterning process mayinclude laser ablation, and the second patterning process may include aplasma etching process. Additional embodiments include first and secondpatterning processes that are the same process. For example, both thefirst and second patterning processes may include a laser ablationprocess. According to such an embodiment, the laser intensity may be thesame for the first and second patterning processes. Alternatively, thefirst and second patterning processes may use different laserintensities. By way of example, and not by way of limitation, theintensity of a laser for a direct laser writing process may be between0.5 J/cm² and 3 J/cm². In an additional embodiment, the via openings110, the contact openings 112, and the line openings 114 may be formedwith a single patterning process.

Referring now to FIG. 1C, a seed layer 130 is formed over the patternedsurfaces 145 with a laser assisted local activation process. Using laserassisted local activation to produce the seed layer allows for the seedlayer 130 to be selectively formed only on the patterned surfaces 145 ofthe dielectric layer 101. Laser assisted local activation of thepatterned surfaces 145 reduces the metallic component of the activatorprecursor present in the dielectric layer 101. By way of example, theactivator precursor is reduced to an oxidation state of zero by removingthe ligands from the metallic element. An example of the reduction ofthe metal component in the activator precursor is provided in Equation 1which shows the reduction of PdCl₂ to Pd⁽⁰⁾.

PdCl₂→Pd⁽⁰⁾+Cl₂   (Equation 1)

In an embodiment, the intensity of the laser during laser assisted localactivation is chosen based on the bond energy of the compound used forthe activator precursor. For example, a lower intensity is needed inorganometallic precursors, such as Pd(acac)₂, because of the lower bondenergy between palladium and carbon compared to the bond energy, forexample, between palladium and chlorine. In embodiments the intensity ofthe laser during laser assisted local activation is lower than the laserintensity needed to ablate the dielectric layer 101. By way of example,and not by way of limitation, an intensity of approximately 0.5 J/cm² orlower is needed to reduce the metallic component to an oxidation stateof zero.

While the seed layer is shown as a continuous layer in FIG. 1C,embodiments are not limited to such configurations. It is noted that theseed layer 130 does not need to be continuous in order to allow forsubsequent metallization with an electroless plating process. As such, aseed layer 130 may include isolated metallic elements dispersed over thepatterned surfaces 145. According to embodiments, the seed layer mayhave a thickness less than 10 Å. By way of example, and not by way oflimitation, the seed layer may have a thickness equal to the thicknessof a single atom of the metallic component.

According to an embodiment, the laser assisted local activation isperformed during the patterning process. For example, when thedielectric layer 101 is patterned with laser ablation, laser assistedlocal activation may be performed simultaneously with the patterningprocess. Additional embodiments include laser assisted local activationthat is performed after the patterning process. For example, a plasmaetching process may be used to form the pattern, and thereafter, thelaser assisted local activation may be performed to form the seed layer130. An additional embodiment may also include laser ablating thedielectric layer 101 to form the pattern with a first laser, and thenusing the first laser in a second pass to perform the localizedactivation of the patterned surfaces 145. In an embodiment, the laserablation may be performed with a first laser and a second laser mayfollow the first laser and perform the localized activation of thepatterned surfaces 145.

Referring now to FIG. 1D, the dielectric layer 101 is metallized with anelectroless plating process. Since the seed layer 130 is selectivelyformed only along the patterned surfaces, metal is only deposited onthose surfaces. Embodiments include electroless plating processes fordepositing copper. As shown, the electroless plating process depositsmetal into vias 110, contact openings 112, and line openings 114 to formconductive vias 131, contacts 132, and lines 134, respectively. In anembodiment, the bath used for the electroless plating process may be asolution comprising a source of metal ions, and a reducing agent. By wayof example, and not by way of limitation, the metal ions may be copperions. In an embodiment, the reducing agent may be formaldehyde ordimethylamine borane (DMAB). According to embodiments, the electrolessplating solution may also comprise complexants, buffers, stabilizers,and/or accelerators, as is known in the art.

A catalyst is needed for reducing the metal ions. As such, when thedielectric layer 101 having a seed layer 130 formed thereon isintroduced into the bath a chemical reduction of metal occurs only onthe portions of the dielectric layer 101 where the seed layer 130 ispresent. An exemplary chemical reaction for electroless plating ofcopper is shown in Equation 2.

Accordingly, the electroless plating process described with respect toFIGS. 1A-1D may be used to selectively plate only the patterned surfacesof a dielectric layer. As shown in FIG. 1D, the top surfaces of thecontacts 132 and lines 134 may be substantially coplanar with the top ofthe unpatterned surfaces 155 of the dielectric layer 101.

According to an additional embodiment, differences in the surfacepotential of patterned surfaces 145 and unpatterned surfaces 155 areused in order to selectively metalize only the patterned surfaces 145.In such embodiments, the dielectric layer is dipped into a seedingsolution and the seed layer deposits from the solution onto thedielectric layer. According to embodiments, the seeding solution may bea colloidal seeding solution or an ionic seeding solution.

Referring now to FIGS. 2A-2B, a process of forming the seed layer 130with a colloidal solution is described according to an embodiment. Asshown in FIG. 2A, a dielectric layer 201 is formed and patterned. Asshown, the dielectric layer 201 may be formed over one or more contacts120 formed on a lower layer. Dielectric layer 201 is substantiallysimilar to the dielectric layer described above with respect to FIG. 1A,with the exception that it does not need to be doped with an activatorprecursor. Dielectric layer 201 may be spun on or laminated over anexisting layer. Embodiments include a cured or partially cureddielectric layer 201. By way of example, and not by way of limitation, apartially cured dielectric layer 201 may be 90% cured. As shown in FIG.2A, the patterned dielectric layer 201 may comprise one or more viaopenings 110 that provide an opening to electrical contacts 120 formedon a lower layer, one or more contact pad openings 112, and one or morecontact line openings 114, or any combination thereof.

According to embodiments, the patterning process used to pattern thedielectric layer 130 increases the surface potential of the patternedsurfaces 145 with respect to the surface potential of the unpatternedsurfaces 155. According to an embodiment, the patterning process is alaser ablation process. The use of laser ablation provides severalmechanisms for increasing the surface potential of the patternedsurfaces 145. For example, photolytic decomposition of the dielectricmaterial in the dielectric layer 201 changes the surface functionalities(e.g., chemical reactivity and/or electrical conductivity) by producingdangling bonds at the laser ablated surface. Since ligands have beenremoved from the dielectric material, the ablated surface is morereactive and will have an increased surface potential. The surfacepotential of the laser ablated surfaces depends on the conformationalorientation of the functional groups and presences of ionic and/orradical fragments that are left at the surface. By way of example, andnot by way of limitation, the exposed functional groups may include C═Ogroups, C—O ester groups, C═N groups, C—H groups from aromatic andaliphatic components, and COOH groups. Additionally, friction causedduring laser ablation produces static charge on the patterned surfaces145 that also increases the surface potential of the patterned surfaces145 relative to the unpatterned surfaces 155.

According to an embodiment, the surface potential of the patternedsurfaces 145 relative to the unpatterned surfaces 155 may be increasedfurther by applying a surface treatment to the dielectric layer 201. Theincrease in surface potential results from the removal of loose debrisfrom the laser ablation process, thereby exposing additional danglingbonds on the patterned surface. According to embodiments, the surfacetreatment includes the application of one or more of deionized water,ethanol, acetone, H₂SO₄, H₂NO₃, or Na-dodecylbenzene sulfonate (SDBS).In an embodiment, the surface treatment may include rinsing the solutionover the surface of the dielectric layer 201. Alternatively, the surfacetreatment may include dipping the dielectric layer 201 into a bath ofthe surface treatment solution. In an embodiment, the surface potentialof the patterned surfaces 145 may be increased by between 100% and 500%after the surface treatment. By way of example, and not by way oflimitation, before a surface treatment, the patterned surfaces 145 mayhave a surface potential between approximately 1 V and 2 V (as measuredby an electrostatic voltmeter) and the surface potential of thepatterned surfaces 145 may be between approximately 4 V and 10 V (asmeasured by an electrostatic voltmeter) after the surface treatment. Inan embodiment that includes applying a deionized water surface treatmentto the surfaces of the dielectric layer 201, the surface potential ofthe unpatterned surfaces 155 of the dielectric layer 201 may beapproximately −1 V (as measured by an electrostatic voltmeter) and thesurface potential of patterned surfaces 145 of the dielectric layer 201may be approximately 10 V (as measured by an electrostatic voltmeter).

After dielectric layer 201 has been patterned and a surface treatmenthas (optionally) been applied, a seed layer is formed over the surfaceof the dielectric layer 201. According to embodiments, the seed layer130 is selectively formed over the patterned surfaces 145, as shown inFIG. 2B, by dipping the dielectric layer 201 into a seeding solution.The increased surface potential of the patterned surfaces 145 causes theseed layer 130 to selectively deposit over the patterned surfaces 145 ofthe dielectric layer 201.

According to an embodiment, a colloidal seeding solution may include asolution including PdSO₄ and H₂SO₄. A seeding solution that includesPdSO₄ and H₂SO₄ results in the formation of negatively charged Pdcolloids. By way of example, the Pd colloids may have an averagediameter between approximately 4 nm and 8 nm. Since the charge of the Pdcolloids is opposite to that of the patterned surface 145, the Pdcolloids selectively deposit onto the positively charged patternedsurfaces 145. Embodiments may also include the application of asurfactant. By way of example, and not by way of limitation, thesurfactant may be SDBS or polyvinyl pyrrolidone (PVP). A surfactant maydecrease the surface tension and improve the coating of the seed layer130 onto the patterned surfaces 145. According to an embodiment, thesurfactant may be applied to the dielectric layer 201 before or afterthe PdSO₄/H₂SO₄ seeding solution has been applied. The deposited Pdcolloids that form the seed layer 130 are capable of catalyzing theelectroless plating process even though the Pd is not reduced to anoxidation state of zero. According to an additional embodiment, the Pdcolloids may be may be reduced to an oxidation state of zero (i.e.,Pd⁽⁰⁾) in order to provide a greater catalyzing effect during theelectroless plating process. The Pd colloids may be reduced to Pd⁽⁰⁾ byapplying a reducing agent to the surfaces of the dielectric layer 201subsequent to the formation of the seed layer 130. By way of example,and not by way of limitation, the reducing agent may be DMABtrimethylamine borane, isopropylamineborane, morpholineborane, sodiumborohydride, potassium borohydride, or hypophosphorus acid.

According to an additional embodiment, a colloidal seeding solutionincludes a mixture of SnCl₂ and PdCl₂. The solution of SnCl₂ and PdCl₂produces a negatively charged colloid that includes Pd and Sn ions. Inan embodiment, the Pd/Sn colloids may have an average diameter between10 nm and 20 nm. The negatively charged colloid selectively deposits onthe positively charged patterned surfaces 145.

Furthermore, Sn⁺² ions readily reduce Pd⁺² ions. As such the Pd colloidsmay also be reduced to an oxidation state of zero by excess Sn⁺² ions inthe solution. Accordingly, there is no need to apply a reducing agent tothe dielectric layer 201 after the seed layer 130 has been depositedonto the surfaces of the dielectric layer 201.

While the seed layer 130 is shown as a continuous layer in FIG. 2B,embodiments are not limited to such configurations. It is noted that theseed layer 130 does not need to be continuous in order to allow forsubsequent metallization with an electroless plating process. As such, aseed layer 130 may include isolated metallic elements or colloidsdispersed over the patterned surfaces 145. According to embodiments, theseed layer may have a thickness less than 10 Å. By way of example, andnot by way of limitation, the seed layer may have a thickness equal tothe thickness of a single atom of the metallic component.

Subsequent to forming the seed layer 130, the dielectric layer 201 ismetallized with an electroless plating process. Since the seed layer 130is selectively formed only along the patterned surfaces, metal is onlydisposed in these areas. Accordingly, additional masking layers that areneeded in traditional SAP processes to shield the seed layer 130 fromunpatterned surfaces 155 are not needed according to embodiments.Embodiments include electroless plating processes for depositing copper.The electroless plating process deposits metal into vias 110, contactopenings 112, and line openings 114 to form conductive vias 131,contacts 132, and lines 134, respectively. As such, a metallizeddielectric layer 201 that is substantially similar to the metallizeddielectric layer 101 illustrated in FIG. 1D is formed. In an embodiment,the bath used for the electroless plating process may be a solutioncomprising a source of metal ions, and a reducing agent. For example,the metal ions may be copper ions. In an embodiment, the reducing agentmay be formaldehyde or DMAB. According to embodiments, the electrolessplating solution may also comprise complexants, buffers, stabilizers,and/or accelerators, as is known in the art.

According to an additional embodiment, the use of a seeding solutionincluding colloids to form the seed layer 130 may not be entirelyselective to the patterned surfaces 145 of the dielectric layer 201, asshown in FIG. 3. For example, the unpatterned surfaces 155 may also havea slightly positive surface potential. As such, negatively chargedcolloids may be deposited over the patterned surfaces 145 and theunpatterned surfaces 155 of the dielectric layer 201. In suchembodiments, portions of the seed layer 130 that are formed onunpatterned surfaces 155 may be removed with a cleaning process prior toelectroless deposition. According to embodiments, the seed layer 130 isable to be selectively removed from the unpatterned surfaces 155 becausethe adhesion between the unpatterned surfaces 155 and the seed layer 130is weaker than the adhesion between the pattern surfaces 145 and theseed layer 130. By way of example, and not by way of limitation, theadhesion strength between the unpatterned surfaces 155 and the seedlayer 130 may be weaker because the unpatterned surfaces 155 have alower surface potential and/or because the unpatterned surfaces providesweaker mechanical anchoring for the seed layer 130.

In certain patterning processes, such as, for example, those thatutilize laser ablation or plasma etching, the patterning process mayincrease the surface roughness of the patterned surfaces. By way ofexample, a laminated dielectric layer that has been partially cured hasa surface roughness (Ra) of approximately 60 nm or less, and the surfaceroughness (Ra) of a laser ablated surface is approximately 200 nm orgreater. The increase in surface roughness of the patterned surfaces 145improves the mechanical anchoring of the seed layer 130 to the patternedsurfaces 145 of the dielectric layer 201.

Accordingly, a surface cleaning process may be used to selectivelyremove the seed layer from the unpatterned surfaces. After removing theseed layer 130 from the unpatterned surfaces 155, the dielectric layer201 is selectively plated with an electroless plating processsubstantially similar to those described above. Accordingly, ametallized dielectric layer 201 is formed that is substantially similarto the dielectric layer 101 illustrated in FIG. 1D. In an embodiment,the cleaning process may include ultra-sonic cleaning, washing with ahigh pressure water jet, or a combination of the two. Additionalembodiments may include a cleaning process that includes washing thesurface with one or more of acetone, NaOH, and HNO₃. In an embodiment,the cleaning process may be performed after the electroless plating. Insuch embodiments, the entire surface of the dielectric layer 101 maymetalized. However, as a result of the weaker adhesion between the seedlayer 130 and the unpatterned surfaces 155, the cleaning process willselectively remove the deposited metal formed over the unpatternedsurfaces 155 of the dielectric layer 201.

Referring now to FIGS. 4A-4D, a process of forming the seed layer 130with an ionic seeding solution is described according to an embodiment.As shown in FIG. 4A, a dielectric layer 201 is formed and patterned. Asshown, the dielectric layer 201 may be formed over one or more contacts120 formed on a lower layer. Dielectric layer 201 is substantiallysimilar to the dielectric layer described above with respect to FIG. 2A.Dielectric layer 201 may be spun on or laminated. Embodiments include acured or partially cured dielectric layer 201. By way of example, apartially cured dielectric layer 201 may be 90% cured. As shown in FIG.4A, the patterned dielectric layer 201 may comprise one or more viaopenings 110 that provide an opening to electrical contacts 120 formedon a lower dielectric layer, one or more contact pad openings 112, andone or more contact line openings 114, or any combination thereof.

According to embodiments, the patterning process used to pattern thedielectric layer 130 increases the surface potential of the patternedsurfaces 145 with respect to the surface potential of the unpatternedsurfaces 155. According to an embodiment, the patterning process is alaser ablation process. The use of laser ablation provides severalmechanisms for increasing the surface potential of the patternedsurfaces. For example, laser ablation may increase the surface potentialand the reactivity of the surface as a result of photolyticdecomposition. Additionally, friction caused during laser ablationproduces static charge on the patterned surfaces 145 that also increasesthe surface potential of the patterned surfaces 145 relative to theunpatterned surfaces 155. Furthermore, certain patterning processes,such as laser ablation or plasma etching, may also increase the surfaceroughness of the patterned surfaces relative to the unpatternedsurfaces. In such embodiments, additional mechanical anchoring isprovided to portions of the seed layer 130 formed on the patternedsurfaces 145, thereby allowing for cleaning processes to be used toselectively remove portions of the seed layer 130 from the unpatternedsurfaces 155.

According to an embodiment, the surface potential of the patternedsurfaces 145 may be increased further by applying a surface treatment.According to embodiments, the surface treatment includes the applicationof a solution comprising one or more of deionized water, ethanol,acetone, H₂SO₄, H₂NO₃, or SDBS. After dielectric layer 201 has beenpatterned and a surface treatment has (optionally) been applied, a seedlayer is formed over the surface of the dielectric layer 201. Accordingto embodiments, the seed layer 130 is formed over the patterned surfaces145 and unpatterned surfaces 155, as shown in FIG. 4B, by dipping thedielectric layer 201 into an ionic seeding solution.

According to an embodiment, an ionic solution may comprise a solution ofPdCl₂ and HCl. The HCl ionizes the PdCl₂ to create Pd⁺² ions. The Pd⁺²ions adsorb to the patterned surfaces 145 and the unpatterned surfaces155 of the dielectric layer 201. According to an embodiment, a reducingagent is applied to the surfaces of the dielectric layer 201 to reducethe Pd⁺² ions to an oxidation state of zero (i.e., Pd⁽⁰⁾). By way ofexample, and not by way of limitation, the reducing agent is DMAB.

In an additional embodiment, an ionic seeding solution may include a twodip process. By way of example, the dielectric layer 201 may be dippedinto a first seeding solution that includes SnCl₂ and then dipped into asecond seeding solution that includes PdCl₂. In such embodiments, the Snions (Sn⁺²) adsorb onto the surfaces of the dielectric layer 201. Thesecond seeding solution includes Pd⁺² ions that are readily reduced to azero oxidation state by the Sn⁺² ions, which are oxidized to Sn⁺⁴. ThePd⁽⁰⁾ replaces the Sn⁺² ions that were adsorbed to the surfaces of thedielectric layer 201, thereby producing a seed layer 130 comprisingPd⁽⁰⁾.

While the seed layer 130 is shown as a continuous layer in FIG. 4B,embodiments are not limited to such configurations. It is noted that theseed layer 130 does not need to be continuous in order to allow forsubsequent metallization with an electroless process. As such, a seedlayer 130 may include isolated metallic elements dispersed over thepatterned surfaces 145. According to embodiments, the seed layer mayhave a thickness less than 10 Å. By way of example, and not by way oflimitation, the seed layer may have a thickness equal to the thicknessof a single atom of the metallic component.

Referring now to FIG. 4C, the dielectric layer 201 is metallized with anelectroless plating process. In an embodiment, the electroless platingprocess is a copper plating process. The bath used for the electrolessplating process may be a solution comprising a source of metal ions,such as copper ions, and a reducing agent, such as formaldehyde or DMAB.The electroless plating solution may also comprise complexants, buffers,stabilizers, and accelerators, as is known in the art.

When the dielectric layer 201 having a seed layer 130 formed thereon isintroduced into the solution a chemical reduction of metal occurs onlyon the portions of the dielectric layer 201 where the seed layer 130 ispresent. Since the seed layer 130 is formed over both the patternedsurfaces 145 and the unpatterned surfaces 155, the plated metal will bedeposited over the entire surface of the dielectric layer 201. As shownin FIG. 4C, excess metal 135 is formed over the unpatterned surfaces 155due to the presence of the seed layer 130. However, the lower adhesionstrength of the seed layer 130 formed over the unpatterned surfaces 155allows for the excess metal 135 to be selectively removed. For example,the excess metal may be removed with a surface cleaning process such asultra-sonic cleaning, washing with a high pressure water jet, or acombination of the two. Additional embodiments may include a cleaningprocess that includes washing the surface with one or more of acetone,NaOH, and HNO₃. After the cleaning process, the top surfaces of thecontacts 132 and lines 134 may be substantially coplanar with the top ofthe unpatterned surfaces 155 of the dielectric layer 201, as shown inFIG. 4D.

In an embodiment, the cleaning process may be performed before theelectroless plating is performed. In such embodiments, the seed layer130 formed over the unpatterned surfaces 155 is removed in substantiallythe same manner described with respect to FIG. 3. Thereafter, anelectroless plating process may be used to selectively metallize thepatterned surfaces 145 of the dielectric layer 201 to produce adielectric layer substantially similar to the one shown in FIG. 4D.

FIG. 5 is an overhead view of a panel 500 including multiple build-upstructures 100 or 200. Each build-up structure 100 or 200 may include aplurality of dielectric layers 101, 201, formed in accordance withembodiments. Accordingly, a plurality of build-up structures may bemanufactured simultaneously. As shown, each build-up structure 100 or200 may be separated by scribe lines 560 to allow for singulation afterthe build-up structures 100 or 200 have been manufactured.

FIG. 6 shows a corresponding cross-sectional view of a package 600 thatincludes a build-up structure 100 or 200. According to an embodiment,the build-up structure 100 includes one or more dielectric layers 101formed in accordance with embodiments. As such, each dielectric layer101 may include electrical interconnects, such as contacts, conductivelines, and conductive vias, as described above. In an embodiment, thebuild-up structure 100 may include a core 680, although otherembodiments may include a coreless design. The core 680 includes vias683 that allow for electrical connections to be made through thebuild-up structure 100. As shown, a chip 684, such as a flip-chip, isconnected to a build-up structure 100 with solder bumps 686. Thelowermost dielectric layer 101 of the build-up structure 100 may bebonded to a board 690, such as a printed circuit board, with solderbumps 688.

FIG. 7 illustrates a computing device 700 in accordance with anembodiment. The computing device 700 houses a board 702. The board 702may include a number of components, including but not limited to aprocessor 704 and at least one communication chip 706. The processor 704is physically and electrically coupled to the board 702. In someimplementations the at least one communication chip 706 is alsophysically and electrically coupled to the board 702. In furtherimplementations, the communication chip 706 is part of the processor704.

Depending on its applications, computing device 700 may include othercomponents that may or may not be physically and electrically coupled tothe board 702. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 706 enables wireless communications for thetransfer of data to and from the computing device 700. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 706 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 700 may include a plurality ofcommunication chips 706. For instance, a first communication chip 706may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 706 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 704 of the computing device 700 includes an integratedcircuit die packaged within the processor 704. In some implementations,the processor 704 is integrated into a package that includes one or morebuild-up structures that have dielectric layers that are selectivelymetalized in accordance with various embodiments. The term “processor”may refer to any device or portion of a device that processes electronicdata from registers and/or memory to transform that electronic data intoother electronic data that may be stored in registers and/or memory.

The communication chip 706 also includes an integrated circuit diepackaged within the communication chip 706. In accordance with anotherembodiment, the communication chip 706 may be integrated into a packagethat includes one or more build-up structures that have dielectriclayers that are selectively metalized in accordance with variousembodiments.

In further implementations, another component housed within thecomputing device 700 that may be integrated into a package that includesone or more build-up structures that have dielectric layers that areselectively metalized in accordance with various embodiments.

In various implementations, the computing device 700 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 700 may be any other electronic device that processes data.

Embodiments include a method for metallizing a dielectric layer,comprising, patterning the dielectric layer to form one or morepatterned surfaces on the dielectric layer, selectively forming a seedlayer on the one or more patterned surfaces of the dielectric layer, andexposing the dielectric layer to an electroless plating bath comprisingmetal ions and a reducing agent, wherein the seed layer is a catalystthat allows the reducing agent to reduce the metal ions, therebyselectively depositing the metal ions on surfaces of the dielectriclayer where the seed layer is formed. Additional embodiments include amethod for metallizing a dielectric layer, wherein the dielectric layeris doped with an activator precursor and wherein forming the seed layercomprises a laser assisted local activation of the activator precursoron the one or more patterned surfaces of the dielectric layer.Additional embodiments include a method for metallizing a dielectriclayer, wherein patterning the dielectric layer comprises a laserablation process. Additional embodiments include a method formetallizing a dielectric layer, wherein the laser ablation and the laserassisted local activation of the activator precursor are performed atthe same time. Additional embodiments include a method for metallizing adielectric layer, wherein the activator precursor is chosen from PdCl₂,PdSO₄, Pd(acac)₂, Pd nano-particles, Ag nano-particles, Cunano-particles, AgCl₂, or RuCl₂. Additional embodiments include a methodfor metallizing a dielectric layer, wherein a surface potential of theone or more patterned surfaces on the dielectric layer is higher than asurface potential of the unpatterned surfaces of the dielectric layer.Additional embodiments include a method for metallizing a dielectriclayer, wherein forming the seed layer on the patterned surfaces of thedielectric layer comprises exposing the dielectric layer to a colloidalseeding solution wherein the seed layer is selectively deposited out ofthe seeding solution and onto the patterned surfaces of the dielectriclayer. Additional embodiments include a method for metallizing adielectric layer, further comprising, applying a surface treatment tothe dielectric layer prior to exposing the dielectric layer to theseeding solution, wherein the surface treatment increases the differencein the surface potentials of the patterned surfaces and the unpatternedsurfaces of the dielectric layer. Additional embodiments include amethod for metallizing a dielectric layer, wherein the surface treatmentcomprises one or more of, deionized water, ethanol, acetone, H₂SO₄,H₂NO₃, or Na-dodecylbenzene sulfonate (SDBS). Additional embodimentsinclude a method for metallizing a dielectric layer, wherein thecolloidal seeding solution comprises a solution of PdSO₄ and H₂SO₄, orSnCl₂ and PdCl₂. Additional embodiments include a method for metallizinga dielectric layer, further comprising applying a surfactant to thesurface of the dielectric layer. Additional embodiments include a methodfor metallizing a dielectric layer, further comprising applying areducing agent to the surface of the dielectric layer subsequent toexposing the dielectric layer to the colloidal seeding solution, whereinthe reducing agent reduces the seed layer to an oxidation state of zero.Additional embodiments include a method for metallizing a dielectriclayer, further comprising cleaning the surface of the dielectric layerwith an ultra-sonic cleaning process, a cleaning the surface of thedielectric layer with a high pressure water jet, or a combination of theultra-sonic cleaning and high pressure water jet cleaning subsequent toexposing the dielectric layer to the colloidal seeding solution.Additional embodiments include a method for metallizing a dielectriclayer, wherein forming the seed layer on the patterned surfaces of thedielectric layer comprises exposing the dielectric layer to an ionicseeding solution wherein the seed layer is selectively deposited out ofthe seeding solution and onto the surfaces of the dielectric layer.Additional embodiments include a method for metallizing a dielectriclayer, wherein the ionic seeding solution comprises PdCl₂ and HCl, andfurther comprises applying a reducing agent to the surface of thedielectric layer subsequent to exposing the dielectric layer to theionic seeding solution, wherein the reducing agent reduces the seedlayer to an oxidation state of zero. Additional embodiments include amethod for metallizing a dielectric layer, further comprising removingthe seed layer from unpatterned surfaces of the dielectric layer byapplying a cleaning solution comprising acetone or nitric acid.

Additional embodiments include a method for metallizing a dielectriclayer, wherein the cleaning solution is applied after metalizing.Additional embodiments include a method for metallizing a dielectriclayer, wherein the seed layer is a non-continuous layer. Additionalembodiments include a method for metallizing a dielectric layer, whereinthe dielectric layer is laminated or spun on over an existing layer.

Embodiments of the invention include a method for metallizing adielectric layer, comprising, patterning the dielectric layer to formone or more patterned surfaces on the dielectric layer, wherein thepatterning process increases the surface potential of the patternedsurfaces such that it has a net positive charge, applying a surfacetreatment to the dielectric layer that further increases the surfacepotential of the patterned surfaces relative to unpatterned surfaces ofthe dielectric layer selectively forming a seed layer only on the one ormore patterned surfaces of the dielectric layer by dipping thedielectric layer in a colloidal seeding solution, wherein the colloidsare negatively charged and are deposited on the positively chargedpatterned surfaces, and exposing the dielectric layer to an electrolessplating bath comprising metal ions and a reducing agent, wherein theseed layer is a catalyst that allows the reducing agent to reduce themetal ions, thereby depositing the metal ions on surfaces of thedielectric layer where the seed layer is formed. Additional embodimentsinclude a method for metallizing a dielectric layer, wherein the surfacetreatment comprises one or more of, deionized water, ethanol, acetone,H₂SO₄, H₂NO₃, or Na-dodecylbenzene sulfonate (SDBS). Additionalembodiments include a method for metallizing a dielectric layer, whereinthe method further comprises cleaning the surface of the dielectriclayer with ultra-sonic cleaning prior to exposing the dielectric layerto an electroless plating bath.

Embodiments of the invention include a dielectric layer comprising, adielectric material formed over one or more first contacts, one or morepatterned surfaces formed into the dielectric layer, wherein at leastone of the patterned surfaces forms a via through the dielectric layerto expose a top surface of a first contact, and one or more secondcontacts formed only over the patterned surfaces of the dielectric layerand electrically coupled to first contacts by one or more of theconductive vias, wherein top surfaces of the second contacts aresubstantially coplanar with a top surface of the dielectric layer.Additional embodiments include a dielectric layer, wherein thedielectric material is doped with an activator precursor. Additionalembodiments include a dielectric layer wherein the activator precursoris chosen from PdCl₂, PdSO₄, Pd(acac)₂, Pd nano-particles, Agnano-particles, Cu nano-particles, AgCl₂, or RuCl₂.

Reference throughout this disclosure to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. The appearance ofthe phrases “in one embodiment” or “in an embodiment” in various placesthroughout this disclosure are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

In the foregoing Detailed Description, various features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments of the inventionrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate embodiment.

It will be readily understood to those skilled in the art that variousother changes in the details, material, and arrangements of the partsand method stages which have been described and illustrated in order toexplain the nature of this invention may be made without departing fromthe principles and scope of the invention as expressed in the subjoinedclaims.

What is claimed is:
 1. A method for metallizing a dielectric layer,comprising: patterning the dielectric layer to form one or morepatterned surfaces on the dielectric layer, wherein the patterningprocess increases the surface potential of the patterned surfaces suchthat it has a net positive charge; applying a surface treatment to thedielectric layer that further increases the surface potential of thepatterned surfaces relative to unpatterned surfaces of the dielectriclayer; selectively forming a seed layer only on the one or morepatterned surfaces of the dielectric layer by dipping the dielectriclayer in a colloidal seeding solution, wherein the colloids arenegatively charged and are deposited on the positively charged patternedsurfaces; and exposing the dielectric layer to an electroless platingbath comprising metal ions and a reducing agent, wherein the seed layeris a catalyst that allows the reducing agent to reduce the metal ions,thereby depositing the metal ions on surfaces of the dielectric layerwhere the seed layer is formed.
 2. The method of claim 1, wherein thesurface treatment comprises one or more of, deionized water, ethanol,acetone, H₂SO₄, H₂NO₃, or Na-dodecylbenzene sulfonate (SDBS).
 3. Themethod of claim 1, wherein the surface treatment includes dipping thedielectric layer into a bath that includes the surface treatmentsolution.
 4. The method of claim 1, wherein the surface treatmentincludes rinsing the surface treatment solution over the surface of thedielectric layer.
 5. The method of claim 1, wherein the surfacepotential of the patterned surfaces of the dielectric layer is increasedby 100% or more after the surface treatment.
 6. The method of claim 1,wherein the patterned surfaces of the dielectric layer have a surfacepotential between approximately 4 V and 10 V, and wherein theunpatterned surfaces of the dielectric layer have a surface potentialbetween approximately 1 V and 2 V.
 7. The method of claim 1, wherein themethod further comprises cleaning the surface of the dielectric layerwith ultra-sonic cleaning prior to exposing the dielectric layer to anelectroless plating bath.
 8. The method of claim 1, wherein the seedlayer is a non-continuous layer.
 9. The method of claim 1, wherein thedielectric layer is laminated or spun on over an existing layer.
 10. Themethod of claim 1, wherein the colloidal seeding solution includes amixture of SnCl₂ and PdCl₂.
 11. The method of claim 10, wherein thecolloids have an average diameter between approximately 10 nm and 20 nm.12. A packaging structure, comprising: a dielectric material formed overone or more first contacts; one or more patterned surfaces formed intothe dielectric layer, wherein at least one of the patterned surfacesforms a via through the dielectric layer to expose a top surface of afirst contact; and one or more second contacts formed only over thepatterned surfaces of the dielectric layer and electrically coupled tofirst contacts by one or more of the conductive vias, wherein topsurfaces of the second contacts are substantially coplanar with a topsurface of the dielectric layer.
 13. The packaging structure of claim12, wherein the dielectric material is doped with an activatorprecursor.
 14. The packaging structure of claim 13, wherein theactivator precursor is chosen from PdCl₂, PdSO₄, Pd(acac)₂, Pdnano-particles, Ag nano-particles, Cu nano-particles, AgCl₂, or RuCl₂.15. The packaging structure of claim 13, wherein a doping concentrationof the activator precursor is approximately 1% by weight or less. 16.The packaging structure of claim 13, wherein the activator precursor isevenly dispersed through the dielectric layer.